Means for improving encoding/decoding of background sounds, primarily intended for digital cellular telephone systems, have been described in Swedish Patent Applications 93 00290-5 and 93 01798-6. These means are primarily designed to handle a situation where the connection between the speech encoder and the speech decoder is close to ideal, in the sense that only a small amount of bit or transmission errors remain after channel decoding. However, since the connection is a radio channel the received signal may contain some bit or transmission errors. In such a case it may be necessary to modify the methods described in the above Swedish patent applications.
An object of the present invention is an apparatus and a method in which so called error concealment is applied to the received signal in order to make the speech decoding more robust or insensitive to transmission errors.